The invention relates to a filter device for the filtration of compressed air comprising a filter means able to be deinstalled for cleaning and/or renewal purposes.
Filter devices of this type are more particularly employed in connection with so-called servicing units which are utilized for processing compressed air within compressed air supply networks. The filter device, which for example may also be combined with a pressure regulator, generally has a principal body adapted to be fitted in the fluid duct arrangement of the compressed air network and on which a cartridge-like filter means is arranged, which cleans the compressed air passing therethrough to clear it of foreign matter.
Problems do occur when machines and equipment connected with the compressed air network are operated despite the filter device having no filter means or a filter means of the wrong type, as a consequence, for instance, of earlier servicing operations. Since the filter device is frequently placed remote from the machines and devices to be operated, visual checking of its actual condition is hardly possible.
One object of the present invention is to provide a filter with which impairments due to there being the wrong or no filter means fitted may be avoided.
In order to achieve this aim the filter device is fitted with a detection means serving for the detection of the filter means and adapted to produce at least one electrical detection signal dependent on the result of detection. In accordance with requirements such detection means can be so designed that it detects the presence and/or absence of a filter means and/or is designed to recognize the currently installed filter means type, the detect signal in the first mentioned case being a simple yes/no signal and in the latter case being a signal specific to the filter means type. In every case the electrical detect signal, dependent on the result of detection, may be further processed in an optimum fashion in order to help avoiding impairments of the machines and devices connected with the respective compressed air network, there being for instance the possibility of producing a detect signal, when no filter means or the wrong type of filter means is fitted, to prevent putting the connected machines and/or devices into operation.
Further advantageous developments of the invention are defined in the dependent claims.
The detection means will conveniently comprise activating means associated with the filter means and which, when the filter device is installed, cooperate directly or indirectly with sensor means provided on the housing of the filter device for producing a detect signal. The sensor means can for example be designed to be mechanically activated or activated without making contact, there being in the latter case for instance means for optical or magnetic activation. Thus it is possible for the sensor means to comprise at least one magnetic field sensitive sensor, which responds to a permanent magnet, which is caused to move on installation and/or deinstallation of a filter means and is moved by same.
The invention further contemplates a structure, in the case of which the activating means directly cooperate with the housing-mounted sensor means. In order to provide an optimum design of sensor device, it is however possible to provide for indirect actuation by causing the activating means to cooperate with the sensor means by the intermediary of a signal transmission means. The signal transmission means can for example be constituted by a sliding plunger moving on the housing and which is able to be slid in the direction of installation and deinstallation of the filter means and is moved during installation and, respectively, deinstallation of the filter means in relation to the sensor means.
In the case of a design which is more especially simple the activating means are constituted by at least one strike face which acts on the signal transmission means and which is provided on the respective filter means.
In order to produce a detect signal specific to the type of filter means, it is possible for the different filter means types to possess different design)s of activating means. In the case of the above mentioned strike faces it is possible in connection with the filter means of different types to provide a different positioning related to the direction of installation and deinstallation with the result that the associated signal transmission means is displaced different distances in relation to the sensor means in a manner dependent on the type of inserted filter means.
Preferably, an electronic evaluating means is provided for the evaluation of the detect signals produce. It may be provided externally and be connected by way of suitable communication means with the filter device. In the case of a particularly compact arrangement the evaluating means is designed as a direct component of the filter device or as a component of a compressed air servicing unit, to which device belongs.
In the case of an advantageous further development of the filter device means are provided for the recognition of the degree of clogging of the filter means currently in use, on the basis of which the time for the necessary replacement or cleaning of the respective filter means may be set. The filter device is in this case mounted in a principal fluid duct, which it divides into an input flow section associated with an inlet and an output flow section associated with an outlet, the recognition means comprising a pressure differential sensor means responsive to the pressure differential between the input flow section and the output flow section and furthermore a flow rate sensor means responsive to the flow rate through the principal fluid duct. The pressure differential and the flow data found are linked in an electronic evaluating means to yield a condition value relevant for the degree of clogging of the filter means, which value may be compared with predetermined limit values. Unlike recognition means based on the detection of the pressure differential alone, it is possible in this manner to ensure that the critical degree of clogging is detected even during operation of the plant having the filter device, even when different flow rates occur owing to switching on and/or off of loads.
The electronic evaluating means preferably comprises a comparison means, in which a comparison is made between the detected condition value and the predetermined limit values, a means being present if desired which renders it possible to store limit values for at least one filter means type. It is particularly advantageous in this case to have a design, in the case of which limit values may be stored for several different types of filter means in the storage means, a selection means being employed to implement a selection of limit values dependent on the filter means type, in the case of which selection the electrical detect signals, supplied by the detection means, being taken into account.
The means for the recognition of the degree of clogging preferably furthermore also include an input pressure sensor means responsive to the input pressure value obtaining in the inlet flow section of the principal fluid duct the detected input pressure value being additionally taken into account in the electronic evaluating means for ascertainment of the instantaneous or current condition value with the result that the filter device may be operated in a universal manner and independently from the instantaneously obtaining input pressure value.
In what follows the invention will be described in detail with reference to the accompanying drawings.